Run Maniphest batch edits through modern editor

Summary:
Ref T2217. Swaps batch edits to modern editor.

Also, fix some issues with required fields and viewers being required to render certain standard fields (notably, date).

Test Plan: Made various batch edits, verified they went through properly.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T2217

Differential Revision: https://secure.phabricator.com/D7083